As apparatuses which detect the presence of an object (a foreign object) sandwiched between a door and a vehicle body, such as a slide door and a back door, there are object detecting apparatuses which include: 1) a pressure-sensitive sensor provided at an outer edge portion of a door for a vehicle; and 2) a signal processing circuit configured to proceed a pressure-sensitive output signal of the pressure-sensitive sensor. Because a pressure-sensitive sensor such as described above is attached to a door portion which comes in contact with an object when an entrapment (which is a state the object is sandwiched between the door and the vehicle body) occurs, a position of the pressure-sensitive sensor inevitably results in an outer edge portion of the vehicle door which faces an opening of the door. In other words, when such entrapment occurs, there is no need to provide the pressure-sensitive sensor at a portion where the sensor cannot come in contact with the object. A signal processing circuit is configured with electric circuits, which achieve some functions such as amplify a pressure-sensitive output signal. A means for determining an entrapment determines the presence of an entrapment of an object on the basis of a processed signal outputted from the signal processing circuit, e.g., based on whether the processed signal is equal to or greater than a predetermined threshold value.
A pressure-sensitive sensor disclosed in Japanese Patent No. 3300660 includes a sensor body and an outer cover surrounding the sensor body. The outer cover, which is made of an elastic material and exhibits a long tubular shape, possesses a cross-shaped bore which extends along a longitudinal direction of the outer cover. The cross-shaped bore is displaced gradually about an axis of the tubular-shape and is provided, therein, with plural electrical leads, which are spaced, from one another and act as a spirally shaped electrode extending along the longitudinal direction of the cross-shaped bore. Once a load (a compressive force) is applied to this pressure-sensitive sensor in response to an entrapment of an object, the outer cover is elastically deformed and the cross-shaped bore inside the outer cover is compressed or crushed. In such circumstances, two from among the plural electrical leads or all of them, which are arranged inside the cross-shaped bore, may come in contact together. As a result, a pressure-sensitive output signal of the pressure-sensitive sensor is changed between when the pressure-sensitive sensor is not subjected with such load and when is subjected therewith. The pressure-sensitive sensor is at a nonconductive state when it is not subjected with such load, while it is at a conductive state when it is subjected with such load. Therefore, a processed signal outputted by the signal processing circuit varies, and the variation, or a value, of the processed signal is referred to by an object detecting means to determine the presence of an entrapment.
An object detecting apparatus disclosed in JP2001-165784A employs, as a pressure-sensitive sensor, a piezoelectric sensor having a piezoelectric material. Once this piezoelectric sensor is applied with a load (a compressive force) in response to an entrapment, polarization occurs at the piezoelectric material, and a pressure-sensitive output signal outputted by the piezoelectric sensor varies. As a result, a processed signal outputted by the signal processing circuit varies, and the variation, or a value, of the processed signal is referred to by an object detecting means to determine the presence of an entrapment.
As described above, whichever type of pressure-sensitive sensor is employed between the sensors disclosed in Japanese Patent No. 3300660 and in JP2001-165784A, an outer edge portion, at which an entrapment may occur, is equipped with a pressure-sensitive sensor, while a portion, which is not associated with an entrapment, is not equipped therewith. The pressure-sensitive sensor is connected to the signal processing circuit via the outer edge portion of the door.
According to conventional object detecting apparatuses including the above described ones, a signal processing circuit is mounted on an outer edge portion of a door for a vehicle, the outer edge portion which is also provided with a pressure-sensitive sensor. However, it is most likely that any particular water preventions have not been applied to such outer edge portions of the vehicle doors, which are equipped with the pressure-sensitive sensors. Accordingly, there is a danger that the signal processing circuit, which is incorporated with electric circuits, may malfunction due to water, or may be damaged.
Further, because the outer edge portion of the door for the vehicle is not shielded from electromagnetic noise, once the signal processing circuit is influenced by electromagnetic noise, there is a danger that an entrapment may not be detected appropriately.
Still further, in order to detect an entrapment of an object appropriately, the pressure-sensitive sensor is required to be mounted from end to end of the vehicle door, which may constrain a space for the signal processing circuit to be mounted on the outer edge portion. Therefore, where detecting performance of an entrapment is to be improved under such constrain, if the signal processing circuit is attempted to be mounted on the outer edge portion of the vehicle door, it is necessary to downsize the signal processing circuit.
As described above, according to conventional object detecting apparatuses, in which signal processing circuits are attempted to be mounted on outer edge portions of a door for a vehicle, a space for the signal processing circuit is limited, and some drawbacks may occur due to water, electromagnetic noise, or the like, drawbacks which include malfunction or erroneous detection of entrapments.
The present invention has been made in view of the above circumstances, and provides an object detecting apparatus, according to which a space-limitation for a signal processing circuit can be avoided, high waterproof level can be attained, and an entrapment can be detected normally without being influenced by disturbances such as noise.